Process for producing unsaturated aliphatic acids

ABSTRACT

The present invention relates to a process for the production of unsaturated aliphatic acids and the catalyst therefor, by the vapor phase oxidation of the corresponding unsaturated aliphatic aldehydes with molecular oxygen, optionally in the presence of steam, in the presence of an oxidation catalyst consisting of the oxides of the elements molybdenum, vanadium, tungsten and lanthanum, and optionally one or more of the oxides of the elements manganese, iron, copper, aluminum, cobalt, nickel, phosphorus, zinc, bismuth, silver, cadmium, niobium, arsenic, chromium, the alkali and the alkaline earth elements.

This is a division of application Ser. No. 691,691 filed June 1, 1976.

BACKGROUND OF THE INVENTION

Catalyst compositions similar to those of the present invention areknown for the oxidation of acrolein to acrylic acid. For example, thedisclosure in U.S. Pat. No. 3,567,773 shows catalyst compositionscontaining the elements of molybdenum, vanadium and tungsten, and GermanPat. No. 2,456,100 discloses catalysts having the composition ofmolybdenum, vanadium and tungsten in combination with such elements ascopper, cobalt and iron. However the catalyst composition of the presentinvention has heretofore not been disclosed.

THE INVENTION

The present invention relates to an improved process for producingolefinically unsaturated carboxylic acids from the correspondingunsaturated aldehydes and to the catalyst composition utilized therefor.More specifically, the present invention relates to a vapor phaseprocess for producing acrylic acid or methacrylic acid from acrolein andmethacrolein, respectively, by oxidation of the unsaturated aldehydeswith molecular oxygen, optionally in the presence of steam, and in thepresence of an oxidation catalyst having the empirical formula:

    Mo.sub.a V.sub.b W.sub.c La.sub.d X.sub.e O.sub.g

wherein X is one or more of the elements selected from the groupconsisting of manganese, iron, copper, zinc, aluminum, cobalt, nickel,phosphorus, cadmium, bismuth, silver, niobium, arsenic, chromium, alkaliand alkaline earth elements, and

wherein the number of atoms of each element present is represented by athrough f,

wherein a is a number from 6 to 18;

b is a number from 0.1 to 10;

c is a number from 0.1 to 6;

d is a number from 0.01 to 5;

e is a number from 0 to 5; and

f is a number that satisfies the valence requirements of the otherelements present.

Preferred catalysts are those wherein a is between 9 and 15; b isbetween 0.5 and 5; c is between 0.5 and 3; d is between 0.05 and 1; ande is between 0 and 1. The elements are present in these catalyticcomposition in the form of their oxides or oxide complexes.

In addition to the active catalytic ingredients, the catalysts of theinvention may contain a support material. Suitable support materialsinclude silica, alumina, zirconia, silicon carbide, boron phosphate andthe like. A preferred support material is alundum.

The catalysts of this invention are highly effective for oxidationreactions such as the oxidation of butadiene to maleic anhydride and theoxidative esterification of unsaturated aldehydes to the correspondingunsaturated ester. Preferred among these oxidative reactions is theproduction of unsaturated acids from the corresponding unsaturatedaldehyde, and more specifically the catalysts of the invention arecapable of very selectively oxidizing acrolein to acrylic acid at lowtemperatures with little or no acetic acid production.

The oxidation of unsaturated aldehydes to obtain the corresponding acidis well known in the art. Basically, the invention, with respect to theprocess, is the use of the new catalyst within the parameters of theknown art process.

The known process involves the contacting of the unsaturated aldehydewith molecular oxygen in the presence of steam at a temperature of about200° to about 500° C. The ratio of the reactants may vary widely, withmolar ratios of molecular oxygen to aldehyde of about 0.5 to about 5normally being employed. Molecular oxygen is most conveniently added asair. The amount of steam may vary widely from the small amount generatedin the reaction to 20 or more moles of steam per mole of aldehyde. Inthe preferred practice of the invention, about 1 to about 10 moles ofsteam are added to the reactant feed.

The reaction may be conducted in a fixed-bed or fluid-bed reactor orforms thereof, using atmospheric, superatmospheric or subatmosphericpressure. The apparent contact time may vary considerably, with contacttimes of a fraction of a second to 20 seconds or more normally beingemployed.

As noted above, catalysts very similar to the catalysts of the inventionare known, see for example U.S. Pat. No. 3,567,773, and thus catalystsof this general type can readily be prepared by persons of ordinaryskill in the art.

Normally, the catalysts of the invention are prepared by mixing thecatalyst ingredients in the proper proportions in an aqueous mixture,drying the resulting aqueous slurry and calcining the product. Theingredients going into the preparation of the catalysts can be theoxides, halides, nitrates, acetates, or other salts of the particularcompound added. If a support is used, the material comprising thesupport is usually incorporated into the catalyst along with the otheringredients. After the catalyst ingredients have been combined to forman aqueous slurry, the slurry is evaporated to dryness, and the driedsolid obtained is heated in the presence of air at temperatures betweenabout 200° and 600° C. This calcination can take place outside of thecatalytic reactor or an in situ activation can be utilized.

There are a number of preparations that can be used to make desirablecatalysts of the invention. A preparation used in the examples is shownin the Specific Embodiments, but it is not to be construed that themethod of preparation is limited to the preparation described.

SPECIFIC EMBODIMENTS Catalyst Preparation

The catalyst of Comparative Example A and the catalysts of Examples 1-4which are representative of the present invention were preparedaccording to the following procedure.

COMPARATIVE EXAMPLE A Catalyst Mo₁₂ V₃ W₁.2 O₄₇.1

To 250 cc of hot distilled water was added 6.16 g of ammoniummetavanadate. After this reagent was dissolved with heating andstirring, 5.84 g of ammonium metatungstate and 37.21 of ammoniumheptamolybdate were added and readily dissolved. The solution wasevaporated to near dryness with continual heating and stirring, and thecontents were then placed in a drying oven at approximately 120° C. for16 hours. The dried material was crushed and ground to pass through a 50mesh screen. A sufficient amount of powder was employed to coat 3/16"alundum spheres to achieve a twenty weight percent coating on thespheres. The coated spheres were then dried at 120° C. for three hoursand then activated by heat treating at 370° C. for two hours.

EXAMPLE 1 Catalyst Mo₁₂ V₃ W₁.2 La₀.5 O₄₇.8

The procedure of Comparative Example A was repeated using the samequantities of the same reagents followed by the addition of 1.43 g oflanthanum oxide (La₂ O₃) and the catalyst completed as described.

EXAMPLE 2 Catalyst Mo₁₂ V₃ W₁.2 La₀.5 Co₀.1 O₄₈.0

The procedure of Composition A was repeated using 4.44 g of ammoniummetavanadate, 4.21 g of ammonium metatungstate, and 26.84 g of ammoniumheptamolybdate, followed by the addition of 1.03 g of lanthanum oxideand 0.315 g of cobalt acetate, and the catalyst completed as described.

EXAMPLE 3 Catalyst Mo₁₂ V₃ W₁.2 La₀.5 Cu₀.2 O₄₈.0

The procedure of Composition A was repeated using 4.43 g of ammoniummetavanadate, 4.20 g of ammonium metatungstate, 26.75 g of ammoniumheptamolybdate, followed by the addition of 1.03 g of lanthanum oxideand 0.50 g of cupric acetate, and the catalyst completed as described.

EXAMPLE 4 Catalyst Mo₁₂ V₃ W₁.2 La₀.5 Mn₀.1 O₄₈.0

The procedure of Composition A was repeated using 4.45 g of ammoniummetavanadate, 4.22 g of ammonium metatungstate, 26.85 g of ammoniumheptamolybdate, followed by the addition of 1.03 g of lanthanum oxide,and 0.31 g of manganese acetate, and the catalyst completed asdescribed.

The catalysts prepared above were placed in a fixed-bed reactorconstructed of 1.0 cm.-inside diameter stainless steel tubing having areaction zone of 20 c.c. The reactor was heated in a split blockfurnace. The reactor was fed with a mixture ofacrolein/air/nitrogen/steam in the molar ratio of 1/8.5/2.5/6. Thereaction was conducted at atmospheric pressure, and an apparent contacttime was two seconds. The temperatures of the surrounding block employedin the reactions are given in Table I, and the results given in theTable are in terms of the following definitions: ##EQU1##

The improved conversions of acrolein to acrylic acid obtained with thecatalyst compositions of the present invention are readily apparent bythe direct comparison of Examples 1-4 with Comparative Example A whichrepresents a catalyst composition of the prior art.

In the same manner as shown by the examples above, other catalysts ofthe invention containing different amounts of lanthanum and differentoptional elements, such as iron, zinc, aluminum, chromium, and the likeare used to produce acrylic acid.

Also using the catalysts of the present invention, maleic anhydride,methacrylic acid or acrylates are produced by known oxidation reactions.

                                      TABLE I                                     __________________________________________________________________________    Oxidation of Acrolein to Acrylic Acid                                                                Reaction                                                                             % Conv. of                                                                          [Corrected.sup.2 % Single Pass Yield                                          of]               % Selec. to             Example No.                                                                           Catalyst Composition.sup.1                                                                   Temp., °C.                                                                    Acrolein                                                                            Acrylic Acid                                                                           Acetic Acid                                                                            Acrylic                 __________________________________________________________________________                                                          Acid                    Comp. A Mo.sub.12 V.sub.3 W.sub.1.2 O.sub.47.1                                                       318    98.1  81.4     2.8      83.0                    1       Mo.sub.12 V.sub.3 W.sub.1.2 La.sub.0.5 O.sub.47.8                                            319    97.0  84.3     2.4      86.9                    2       Mo.sub.12 V.sub.3 W.sub.1.2 La.sub.0.5 Co.sub.0.1 O.sub.48.0                                 342    98.5  87.7     2.6      89.0                    3       Mo.sub.12 V.sub.3 W.sub.1.2 La.sub.0.5 Cu.sub.0.2 O.sub.48.0                                 320    99.9  91.3     2.1      91.3                    4       Mo.sub.12 V.sub.3 W.sub.1.2 La.sub.0.5 Mn.sub.0.1 O.sub.48.0                                 348    97.0  85.4     2.7      88.0                    __________________________________________________________________________     .sup.1 20% active catalyst component coated on 3/16" Alundum spheres.         .sup.2 Corrected to 100% carbon balance.                                 

We claim:
 1. The process for the oxidation of acrolein or methacroleinto acrylic acid or methacrylic acid, respectively, in the vapor phasewith molecular oxygen, optionally in the presence of steam, at atemperature in the range of about 200° to about 500° C. employing acatalyst having the empirical formula:

    Mo.sub.a V.sub.b W.sub.e La.sub.d X.sub.e O.sub.f

wherein X is one or more of the elements selected from the groupconsisting of manganese, iron, copper, zinc, aluminum, cobalt, nickel,cadmium bismuth, the alkali and the alkaline earth elements; and whereinthe number of atoms of each element present is represented by a throughf wherein a is a number from 6 to 18; b is a number from 0.1 to 10; c isa number from 0.1 to 6; d is a number from 0.01 to 5; e is a number from0 to 5; and f is a number that satisfies the valence requirements of theother elements present.
 2. The process in claim 1 wherein acrylic acidis prepared from acrolein.
 3. The process in claim 1 wherein in thecatalyst formula e is zero.
 4. The process in claim 1 wherein in thecatalyst formula a=9 to 15; b=0.5 to 5; c=0.5 to 3; d=0.05 to 1; e=0 to1; and f is a number that satisfies the valence requirements of theother elements present.
 5. The process in claim 1 wherein methacrylicacid is prepared from methacrolein.
 6. The process in claim 1 wherein Xin the catalyst formula is copper.
 7. The process of claim 1 wherein Xin the catalyst formula is cobalt.